Functionalized elastomer nanocomposite

ABSTRACT

An embodiment of the present invention is a nanocomposite comprising a clay and an elastomer comprising at least C 2  to C 10  olefin derived units; wherein the elastomer also comprises functionalized monomer units pendant to the elastomer. Desirable embodiments of the elastomer include poly(isobutylene-co-p-alkylstyrene) elastomers and poly(isobutylene-co-isoprene) elastomers, which are functionalized via Friedel-Crafts reaction with a Lewis acid and a functionalizing agent such as acid anhydrides and/or acylhalides. The clay is exfoliated in one embodiment by the addition of exfoliating agents such as alkyl amines and silanes to the clay. The composition can include secondary rubbers such as general purpose rubbers, and curatives, fillers, and the like. The nanocomposites of the invention have improved air barrier properties such as are useful for tire innerliners and innertubes.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Provisional Application No.60/394,098, filed Jul. 5, 2002, the disclosure of which is incorporatedby reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to nanocomposites comprising clays andelastomers. More particularly, the present invention relates tonanocomposites suitable for air barriers that are a blend of a clay anda functionalized phenyl-containing, or styrenic-based, elastomer,wherein the functionalization may be carried out via Friedel-Craftsreaction.

BACKGROUND OF THE INVENTION

Nanocomposites are polymer systems containing inorganic particles withat least one dimension in the nanometer range. Elastomers comprisingphenyl groups including, for example, styrenic-based elastomerscomprising at least one styrene or substituted styrene unit therein, areone type of elastomer that can be incorporated into a nanocomposite.Some examples of these are disclosed in U.S. Pat. Nos. 6,060,549,6,103,817, 6,034,164, 5,973,053, 5,936,023, 5,883,173, 5,807,629,5,665,183, 5,576,373, and 5,576,372. A common type of inorganic particleused in nanocomposites are phyllosilicates, an inorganic substance fromthe general class of so called “nano-clays” or “clays”. Ideally,intercalation should take place in the nanocomposite, wherein thepolymer inserts into the space or gallery between the clay surfaces.Ultimately, it is desirable to have exfoliation, wherein the polymer isfully dispersed with the individual nanometer-size clay platelets. Dueto the general enhancement in air barrier qualities of various polymerblends when clays are present, there is a desire to have a nanocompositewith low air permeability; especially a dynamically vulcanized elastomernanocomposite such as used in the manufacture of tires.

One method to improve nanocomposite performance is to use functionalizedpolymers blended with clay. This approach has been limited to materialsthat are soluble in water or to materials that can be incorporated intothe polymerization reaction. This approach has been used to preparenylon nanocomposites, using for example, oligomeric and monomericcaprolactam as the modifier. Polyolefin nanocomposites, such aspolypropylene nanocomposites, have utilized maleic anhydride graftedpolypropylenes to achieve some success in the formation ofnanocomposites.

To form articles such as air barriers, it is desirable to use elastomerssuch as isobutylene-based elastomers, for example,poly(isobutylene-co-p-alkylstyrene) elastomers andpoly(isobutylene-co-isoprene) elastomers. While these elastomers havebeen functionalized in order to improve compatibility orcross-linkability with other polymers, suitability of suchfunctionalized polymers for nanocomposites has not been demonstrated ordisclosed. See, for example, U.S. Pat. Nos. 6,372,855 B1; 6,015,862;5,849,828; 5,480,810; 5,814,707; 5,700,871; 5,498,673; 5,356,950; JP11323023 (98 JP-130725 A); EP 0 787 157 B1; and Liu et al., 43 POLYMERBULLETIN 51-58 (1999). What would be desirable is to provide an improvedair barrier using such nanomposites that include these styrenic-basedelastomers, thus improving upon the air barrier qualities that exist forthese elastomers.

Another background reference includes DE 198 42 845 A.

SUMMARY OF THE INVENTION

The present invention provides a nanocomposite comprising suitable forair barrier applications, the nanocomposite comprising a blend of clayand an elastomer comprising C₂ to C₁₀ olefin derived units; wherein theelastomer also comprises functionalized monomer units pendant to theelastomer. Desirable embodiments of the elastomer includepoly(isobutylene-co-p-alkylstyrene) elastomers andethylene-propylene-alkylstyrene rubber, which are functionalized viaFriedel-Crafts reaction with a Lewis acid and a functionalizing agentsuch as acid anhydrides and/or acylhalides. The clay is exfoliated inone embodiment by the addition of exfoliating agents such as alkylamines and silanes to the clay. The composition can include secondaryrubbers such as general purpose rubbers, and curatives, fillers, and thelike. The nanocomposites of the invention have improved air barrierproperties such as are useful for tire innerliners and innertubes.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a nanocomposite material suitable for airbarriers such as innerliners and innertubes for transportation vehicles,trucks, automobiles, and the like. In one aspect of the invention, thenanocomposite comprises clay, preferably swellable clay, and morepreferably exfoliated clay, and an elastomer comprising C₂ to C₁₀ olefinderived units (which includes isoolefin derived units); wherein theelastomer also comprises functionalized monomer units described by thefollowing groups (I), (II), (III), (IV) and (V) pendant to theelastomer, E:

wherein R¹ is selected from hydrogen, C₁ to C₂₀ alkyls, alkenyls oraryls, substituted C₁ to C₂₀ alkyls, alkenyls or aryls; wherein thevalue of x ranges from 0 to 20, preferably from 1 to 10, and morepreferably from 1 to 5; and wherein the value of y ranged from 0 to 20,preferably from 0 to 10; and wherein the value of z ranges from 1 to 20,preferably from 1 to 10, and more preferably from I to 5; and wherein“A” is selected from an alkyl, alkenyl, and aryl group, any of which areeither substituted or not.

Alternately, the nanocomposite of the present invention can be describedas blend of clay and the reaction product of contacting an elastomercomprising C₂ to C₁₀ olefin derived units, an grafling promoter such as,for example, a Lewis acid, and at least one functionalizing compound,such as, for example, an acid anhydride, acylhalide, or blend thereof.In any case, the clay may be a swellable clay in one embodiment, or anexfoliated clay in another embodiment, wherein the clay is exfoliatedwith an exfoliating additive such as an amine or silane compound, asdescribed herein.

The elastomer may be any suitable elastomer as described herein,desirably isobutylene elastomers such aspoly(isobutylene-co-p-alkylstyrene) elastomers and EP rubber such aspoly(ethylene-co-propylene-co-methylstyrene). These are describedfurther below. The nanocomposite may also include other secondaryrubbers, fillers, and curatives, and may be cured by such means as, forexample, heating, to form an article of manufacture that is suitable forair barriers, etc.

The various aspects of the nanocomposite and its use as an air barrierare described more particularly herein, wherein the various embodimentsdescribed for each component are attributable to the various aspects andembodiments of the invention.

As used herein, in reference to Periodic Table “Groups”, the newnumbering scheme for the Periodic Table Groups are used as in HAWLEY'SCONDENSED CHEMICAL DICTIONARY 852 (13th ed. 1997).

The term “elastomer”, as used herein, refers to any polymer orcomposition of polymers consistent with the ASTM D1566 definition. Theterm “elastomer” may be used interchangeably with the term “rubber”, asused herein.

As used herein, the term “alkyl” refers to a paraffinic hydrocarbongroup which may be derived from an alkane by dropping one or morehydrogens from the formula, such as, for example, a methyl group, or CH₃⁻, or an ethyl group, CH₃CH₂ ⁻, etc.

As used herein, the term “alkenyl” refers to an unsaturated paraffinichydrocarbon group which may be derived from an alkane by dropping one ormore hydrogens from the formula, such as, for example, an ethenyl group,CH₂═CH⁻, and a propenyl group, or CH₃CH═CH⁻, etc.

As used herein, the term “aryl” refers to a hydrocarbon group that formsa ring structure characteristic of aromatic compounds such as, forexample, benzene, naphthalene, phenanthrene, anthracene, etc., andtypically possess alternate double bonding (“unsaturation”) within itsstructure. An aryl group is thus a group derived from an aromaticcompound by dropping one or more hydrogens from the formula such as, forexample, phenyl, or C₆H₅ ⁻.

By “substituted”, it is meant substitution of at least one hydrogengroup by at least one substituent selected from, for example, halogen(chlorine, bromine, fluorine, or iodine), amino, nitro, sulfoxy(sulfonate or alkyl sulfonate), thiol, alkylthiol, and hydroxy; alkyl,straight or branched chain having 1 to 20 carbon atoms which includesmethyl, ethyl, propyl, tert-butyl, isopropyl, isobutyl, etc.; alkoxy,straight or branched chain alkoxy having 1 to 20 carbon atoms, andincludes, for example, methoxy, ethoxy, propoxy, isopropoxy, butoxy,isobutoxy, secondary butoxy, tertiary butoxy, pentyloxy, isopentyloxy,hexyloxy, heptryloxy, octyloxy, nonyloxy, and decyloxy; haloalkyl, whichmeans straight or branched chain alkyl having 1 to 20 carbon atoms whichis substituted by at least one halogen, and includes, for example,chloromethyl, bromomethyl, fluoromethyl, iodomethyl, 2-chloroethyl,2-bromoethyl, 2-fluoroethyl, 3-chloropropyl, 3-bromopropyl,3-fluoropropyl, 4-chlorobutyl, 4-fluorobutyl, dichloromethyl,dibromomethyl, difluoromethyl, diiodomethyl, 2,2-dichloroetbyl,2,2-dibromomethyl, 2,2-difluoroethyl, 3,3-dichloropropyl,3,3-difluoropropyl, 4,4-dichlorobutyl, 4,4-difluorobutyl,trichloromethyl, 4,4-difluorobutyl, trichloromethyl, trifluoromethyl,2,2,2-trifluoroethyl, 2,3,3-trifluoropropyl, 1,1,2,2-tetrafluoroethyl,and 2,2,3,3-tetrafluoropropyl. Thus, for example, an example of a“substituted styrenic unit” would include p-methylstyrene,p-ethylstyrene, etc.

Elastomer

Elastomers suitable for use in the present invention comprise C₂ to C₁₀olefin derived units. As used herein, the term “olefin” includes“isoolefins” such as, for example, isobutylene, as well as“multiolefins” such as, for example, isoprene. Preferably, the elastomeralso comprises monomer units having phenyl groups pendant to theelastomer backbone, the phenyl groups either substituted or not. Morepreferably, the elastomer also comprises styrenic derived units selectedfrom styrenes and substituted styrenes, non-limiting examples of whichinclude α-methylstyrene, o-(ortho), m-(meta), and p(para)-methylstyrene, o-, m-, and p-tert-butylstyrene, etc.

In one embodiment of the invention, the elastomer is a random copolymerof units selected from C₂ to C₁₀ olefin derived units (hereinafter,ethylene or “C₂” is referred to as an olefin derived unit) and styrenicderived unit such as, for example p-alkylstyrene derived units; whereinthe p-alkylstyrene derived units are preferably p-methylstyrenecontaining at least 80%, more preferably at least 90% by weight of thep-isomer. In another embodiment of the invention, the elastomer is arandom copolymer of a C₄ to C₇ isoolefin, such as isobutylene, and astyrenic monomer, such as a p-alkylstyrene comonomer, preferablyp-methylstyrene containing at least 80%, more preferably at least 90% byweight of the p-isomer. In yet another embodiment, the elastomer is acopolymer of a isoolefin such as isobutylene and a multiolefin such asisoprene, or “butyl” rubber.

In one embodiment of the-invention, the elastomer may be a copolymer ofstyrenic derived units and/or substituted styrenic derived units, andolefin derived units as described above. The styrene derived units arepresent from 3 wt % to 20 wt % based on the total weight of the polymerin one embodiment, from 5 wt % to 12 wt % in another embodiment, from 5wt % to 15 wt % in yet another embodiment, and from 8 wt % to 13 wt % inyet another embodiment, wherein a desirable range of styrene derivedunit may include any upper wt % limit with any lower wt % limitdescribed herein. The olefin is present in the elastomer in a range offrom 70 wt % to 99.5 wt % by weight of the elastomer in one embodiment,and 85 wt % to 99.5 wt % in another embodiment. Suitable olefins areselected from C₂ to C₁₀ olefins, non-limiting examples of which includeethylene, propene, 1-butene, isobutylene (an isoolefin), 1-hexene,1-octene, cyclopentadiene (a multiolefin) and isoprene (a multiolefin).For example, one embodiment of a suitable elastomer for nanocompositesof the invention may be a copolymer or terpolymer of any one or two ofthese monomers with a styrenic monomer such as, for example,a-methylstyrene, o-methylstyrene, m-methylstyrene, and p-methylstyrenemonomers.

Non-limiting examples of elastomers that are suitable for thenanocomposite of the invention include any one or a mixture of naturalrubber, poly(isobutylene-co-isoprene), polybutadiene,poly(styrene-co-butadiene), poly(isoprene-co-butadiene),poly(styrene-isoprene-butadiene),poly(isoprene-isobutylene-alkylstyrene), star-branched polyisobutylenerubber, poly(isobutylene-co-p-methylstyrene),ethylene-propylene-alkylstyrene rubber, ethylene-propylene-styrenerubber, wherein reference to an “alkyl” includes any C₁ to C₁₀ straightor branched chain alkyl.

In one embodiment of the invention, the elastomer suitable for thenanocomposite is a non-halogenated elastomer, meaning that the elastomerhas not been subjected to a halogenation process, or otherwise comprisehalogen moieties.

An example of a suitable elastomer for use in the present invention ispoly(isobutylene-co-p-methylstyrene), or “XP50” (ExxonMobil ChemicalCompany, Houston Tex.). These isoolefin copolymers, their method ofpreparation and cure are more particularly disclosed in U.S. Pat. No.5,162,445. These elastomers have a substantially homogeneouscompositional distribution such that at least 95% by weight of thepolymer has a p-alkylstyrene content within 10% of the averagep-alkylstyrene content of the polymer. Desirable copolymers are alsocharacterized by a molecular weight distribution (Mw/Mn) of between 2and 20 in one embodiment, and less than 10 in another embodiment, andless than 5 in another embodiment, and less than 2.5 in yet anotherembodiment, and greater than 2 in yet another embodiment; a preferredviscosity average molecular weight in the range of from 200,000 up to2,000,000 and a preferred number average molecular weight in the rangeof from 25,000 to 750,000 as determined by gel permeationchromatography.

The “elastomer”, as described herein, may also comprise a composition ofone or more of the same elastomer having differing molecular weights toyield a composition having a bimodal molecular weight distribution. Thisbimodal distribution can be achieved by, for example, having a lowmolecular weight component in the elastomer. This can be accomplished byphysically blending two different MW polymers together, or by in situreactor blending. In one embodiment, the elastomer has a low molecularweight (weight average molecular weight) component of from 5,000 MW to80,000 MW in one embodiment, and from 10,000 MW to 60,000 MW in anotherembodiment; the low molecular weight component comprising from 5 to 40wt % of the composition in one embodiment, and from 10 to 30 wt % of thecomposition in another embodiment.

In an embodiment comprising poly(isobutylene-co-p-methylstyrene) as theelastomer, the p-methylstyrene derived units are present from 3 wt % to15 wt % based on the total weight of the polymer, and from 5 wt % to 12wt % in another embodiment, and from 8 wt % to 13 wt % in yet anotherembodiment, wherein a desirable range of p-methylstyrene may include anyupper wt % limit with any lower wt % limit described herein. Theisobutylene derived units are present in the elastomer in a range from70 to 99.5 wt % by weight of the elastomer in one embodiment, and 85 to99.5 wt % in another embodiment.

In another embodiment, the elastomer suitable for use in thenanocomposite of the invention is a copolymer of an isomonoolefin (orisoolefin) and a multiolefin, or a “butyl” rubber. In one embodiment ofthe invention, the elastomer is a copolymer of a C₄ to C₆ isoolefin anda multiolefin. In another embodiment, the elastomer is a blend of apolydiene or block copolymer, and a copolymer of a C₄ to C₆ isoolefinand a conjugated, or a “star-branched” butyl polymer. The butylelastomer useful in the present invention can thus be described ascomprising C₄ to C₇ isoolefin derived units and multiolefin derivedunits, and includes both “butyl rubber” and so called “star-branched”butyl rubber.

As used herein, “butyl rubber” refers to both butyl rubber and so-called“star-branched” butyl rubber, described below. Preferably, the olefinpolymerization feeds employed in producing the butyl rubber of theinvention are those olefinic compounds conventionally used in thepreparation of butyl-type rubber polymers. Butyl polymers may beprepared by reacting a comonomer mixture, the mixture having at least(I) a C₄ to C₆ isoolefin monomer component such as isobutylene with (2)a multiolefin, or conjugated diene, monomer component. The isoolefin isin a range from 70 wt % to 99.5 wt % by weight of the total comonomermixture in one embodiment, and 85 wt % to 99.5 wt % in anotherembodiment. The multiolefin component in one embodiment is present inthe comonomer mixture from 30 to 0.5 wt % in one embodiment, and from 15wt % to 0.5 wt % in another embodiment. In yet another embodiment, from8 wt % to 0.5 wt % of the comonomer mixture is multiolefin.

Suitable isoolefins include C₄ to C₇ compounds such as isobutylene,isobutene, 2-methyl-1-butene, 3-methyl-1-butene, 2-methyl-2-butene, and4-methyl-1-pentene. The multiolefin is a C₄ to C₁₄ conjugated diene suchas isoprene, butadiene, 2,3-dimethyl-1,3-butadiene, myrcene,6,6-dimethyl-fulvene, cyclopentadiene, hexadiene and piperylene. Oneembodiment of a butyl rubber suitable for use in the invention comprisesfrom 92 wt % to 99.5 wt % of isobutylene and from 0.5 wt % to 8 wt %isoprene, and from 95 wt % to 99.5 wt % isobutylene and 0.5 wt % to 5.0wt % isoprene in yet another embodiment.

The star-branched butyl rubber is a composition of a butyl rubber,either halogenated or not, and a polydiene or block copolymer, eitherhalogenated or not. The polydienes/block copolymer, or branching agents(hereinafter “polydienes”), are typically cationically reactive and arepresent during the polymerization of the butyl rubber, or can be blendedwith the butyl or butyl rubber to form the star-branched butyl rubber.

More particularly, star-branched butyl rubber is typically a compositionof the butyl and a copolymer of a polydiene and a partially hydrogenatedpolydiene selected from the group including styrene, polybutadiene,polyisoprene, polypiperylene, natural rubber, styrene-butadiene rubber,ethylene-propylene diene rubber, styrene-butadiene-styrene andstyrene-isoprene-styrene block copolymers. These polydienes are present,based on the monomer wt %, greater than 0.3 wt % in one embodiment, andfrom 0.3 wt % to 3 wt % in another embodiment, and from 0.4 wt % to 2.7wt % in yet another embodiment.

The elastomer or functionalized elastomer is present in thenanocomposite of the invention from 10 to 100 phr in one embodiment,from 20 to 80 phr in another embodiment, and from 30 to 70 phr in yetanother embodiment, wherein a desirable range may be any combination ofany upper phr limit with any lower phr limit.

Clay

Compositions of the invention include at least one functionalizedelastomer blended by any suitable means with at least one clay, aswellable clay in one embodiment, which may or may not be exfoliatedusing an exfoliating agent. Swellable clay materials suitable for thepurposes of this invention include natural or synthetic phyllosilicates,particularly smectic clays such as montmorillonite, nontronite,beidellite, volkonskoite, laponite, hectorite, saponite, sauconite,magadite, kenyaite, stevensite and the like, as well as vermiculite,halloysite, aluminate oxides, hydrotalcite and the like. These swellableclays generally comprise particles containing a plurality of silicateplatelets having a thickness of 8-12 Å, and contain exchangeable cationssuch as Na⁺, Ca⁺², K⁺ or Mg⁺² present at the interlayer surfaces.

The swellable clay may be exfoliated by treatment with organic molecules(swelling or exfoliating “agents” or “additives”) capable of undergoingion exchange reactions with the cations present at the interlayersurfaces of the layered silicate. Suitable exfoliating agents includecationic surfactants such as ammonium, alkylamines or alkylammonium(primary, secondary, tertiary and quaternary), phosphonium or sulfoniumderivatives of aliphatic, aromatic or arylaliphatic amines, phosphinesand sulfides. Desirable amine compounds (or the corresponding ammoniumion) are those with the structure R²R³R⁴N, wherein R², R³, and R⁴ are C₁to C₃₀ alkyls or alkenes in one embodiment, C₁ to C₂₀ alkyls or alkenesin another embodiment, which may be the same or different. In oneembodiment, the exfoliating agent is a so called long chain tertiaryamine, wherein at least R² is a C₁₄ to C₂₀ alkyl or alkene.

Another class of exfoliating agents include those which can becovalently bonded to the interlayer surfaces. These include polysilanesof the structure —Si(R⁵)₂R⁶ where R⁵ is the same or different at eachoccurrence and is selected from alkyl, alkoxy or oxysilane and R⁶ is anorganic radical compatible with the matrix polymer of the composite.

Other suitable exfoliating agents include protonated amino acids andsalts thereof containing 2-30 carbon atoms such as 12-aminododecanoicacid, epsilon-caprolactam and like materials. Suitable swelling agentsand processes for intercalating layered silicates are disclosed in U.S.Pat. Nos. 4,472,538, 4,810,734, 4,889,885 as well as WO92/02582.

In one embodiment, the exfoliating agents includes all primary,secondary and tertiary amines and phosphines; alkyl and aryl sulfidesand thiols; and their polyfunctional versions. Desirable additivesinclude: long-chain tertiary amines such as N,N-dimethyl-octadecylamine,N,N-dioctadecyl-methylamine, so called dihydrogenatedtallowalkyl-methylamine and the like, and amine-terminatedpolytetrahydrofuran; long-chain thiol and thiosulfate compounds likehexamethylene sodium thiosulfate.

The exfoliating additive such as described herein is present in thecomposition in an amount to achieve optimal air retention as measured bythe permeability testing described herein. For example, the additive maybe present from 0.1 to 20 phr in one embodiment, and from 0.2 to 15 phrin another embodiment, and from 0.3 to 10 phr in yet another embodiment.The exfoliating agent, if present, may be added to the composition atany stage; for example, the additive may be added to the interpolymer,followed by addition of the clay, or may be added to the elastomer andclay mixture; or the additive may be first blended with the clay,followed by blending with the interpolymer in yet another embodiment.

In another embodiment of the invention, improved elastomerimpermeability is achieved by the presence of at least onepolyfunctional curative. An embodiment of such polyfunctional curativescan be described by the formula Z—R⁷—Z′, wherein R⁷ is one of a C₁ toC₁₅ alkyl, C₂ to C₁₅ alkenyl, and C₆ to C₁₂ cyclic aromatic moiety,substituted or unsubstituted; and Z and Z′ are the same or different andare one of a thiosulfate group, mercapto group, aldehyde group,carboxylic acid group, peroxide group, alkenyl group, or other similargroup that is capable of crosslinking, either intermolecularly orintramolecularly, one or more strands of a polymer having reactivegroups such as unsaturation. So-called bis-thiosulfate compounds are anexample of a desirable class of polyfunctional compounds included in theabove formula. Non-limiting examples of such polyfunctional curativesare as hexamethylene bis(sodium thiosulfate) and hexamethylenebis(cinnamaldehyde), and others are well known in the rubber compoundingarts. These and other suitable agents are disclosed in, for example, theBLUE BOOK, MATERIALS, COMPOUNDING INGREDIENTS, MACHINERY AND SERVICESFOR RUBBER (Don. R. Smith, ed., Lippincott & Peno Inc. 2001). Thepolyfunctional curative, if present, may be present in the compositionfrom 0.1 to 8 phr in one embodiment, and from 0.2 to 5 phr in yetanother embodiment.

Treatment with the exfoliating agents described above results inintercalation or “exfoliation” of the layered platelets as a consequenceof a reduction of the ionic forces holding the layers together andintroduction of molecules between layers which serve to space the layersat distances of greater than 4 Å, preferably greater than 9 Å. Thisseparation allows the layered silicate to more readily sorbpolymerizable monomer material and polymeric material between the layersand facilitates further delamination of the layers when the intercalateis shear mixed with matrix polymer material to provide a uniformdispersion of the exfoliated layers within the polymer matrix.

The amount of clay or exfoliated clay incorporated in the nanocompositesin accordance with an embodiment of the invention is sufficient todevelop an improvement in the mechanical properties and barrierproperties of the nanocomposite, for example, tensile strength or oxygenpermeability. Amounts generally will range from 0.1 wt % to 50 wt % inone embodiment, and from 0.5 wt % to 10 wt % in another embodiment, andfrom 0.5 wt % to 15 wt % in another embodiment, and from 1 wt % to 30 wt% in yet another embodiment, and from 1 wt % to 5 wt % in yet anotherembodiment, based on the polymer content of the nanocomposite. Expressedin parts per hundred rubber, the clay or exfoliated clay may be presentfrom 1 to 30 phr in one embodiment, and from 5 to 20 phr in anotherembodiment. In one embodiment, the exfoliated clay is analkylamine-exfoliated clay.

Secondary Rubber Component

A secondary rubber, or “general purpose rubber” component may be presentin compositions and end use articles of the present invention. Theserubbers may be blended by any suitable means with the elastomer orelastomer/clay composition. These rubbers include, but are not limitedto, natural rubbers, polyisoprene rubber, poly(styrene-co-butadiene)rubber (SBR), polybutadiene rubber (BR), poly(isoprene-co-butadiene)rubber (IBR), styrene-isoprene-butadiene rubber (SIBR),ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM),polysulfide, nitrile rubber, propylene oxide polymers, star-branchedbutyl rubber and halogenated star-branched butyl rubber, brominatedbutyl rubber, chlorinated butyl rubber, star-branched polyisobutylenerubber, star-branched brominated butyl (polyisobutylene/isoprenecopolymer) rubber; poly(isobutylene-co-p-methylstyrene) and halogenatedpoly(isobutylene-co-p-methylstyrene), such as, for example, terpolymersof isobutylene derived units, p-methylstyrene derived units, andp-bromomethylstyrene derived units, and mixtures thereof.

A desirable embodiment of the secondary rubber component present isnatural rubber. Natural rubbers are described in detail by Subramaniamin RUBBER TECHNOLOGY 179-208 (Maurice Morton, ed., Chapman & Hall 1995).Desirable embodiments of the natural rubbers of the present inventionare selected from Malaysian rubber such as SMR CV, SMR 5, SMR 10, SMR20, and SMR 50 and mixtures thereof, wherein the natural rubbers have aMooney viscosity at 100° C. (ML 1+4) of from 30 to 120, more preferablyfrom 40 to 65. The Mooney viscosity test referred to herein is inaccordance with ASTM D- 1646.

Polybutadiene (BR) rubber is another desirable secondary rubber usefulin the composition of the invention. The Mooney viscosity of thepolybutadiene rubber as measured at 100° C. (ML 1+4) may range from 35to 70, from 40 to about 65 in another embodiment, and from 45 to 60 inyet another embodiment. Some commercial examples of these syntheticrubbers useful in the present invention are NATSYN™ (Goodyear ChemicalCompany), and BUDENE™ 1207 or BR 1207 (Goodyear Chemical Company). Adesirable rubber is high cis-polybutadiene (cis-BR). By“cis-polybutadiene” or “high cis-polybutadiene”, it is meant that1,4-cis polybutadiene is used, wherein the amount of cis component is atleast 95%. An example of high cis-polybutadiene commercial products usedin the composition BUDENE™ 1207.

Rubbers of ethylene and propylene derived units such as EPM and EPDM arealso suitable as secondary rubbers. Examples of suitable comonomers inmaking EPDM are ethylidene norbornene, 1,4-hexadiene, dicyclopentadiene,as well as others. These rubbers are described in RUBBER TECHNOLOGY260-283 (1995). A suitable ethylene-propylene rubber is commerciallyavailable as VISTALON™ (ExxonMobil Chemical Company, Houston Tex.).

In another embodiment, the secondary rubber is a halogenated rubber aspart of the terpolymer composition. The halogenated butyl rubber isbrominated butyl rubber, and in another embodiment is chlorinated butylrubber. General properties and processing of halogenated butyl rubbersare described in THE VANDERBILT RUBBER HANDBOOK 105-122 (Robert F. Ohmed., R. T. Vanderbilt Co., Inc. 1990), and in RUBBER TECHNOLOGY 311-321(1995). Butyl rubbers, halogenated butyl rubbers, and star-branchedbutyl rubbers are described by Edward Kresge and H. C. Wang in 8KIRK-OTHMER ENCYCLOPEDIA OF CHEMICAL TECHNOLOGY 934-955 (John Wiley &Sons, Inc. 4th ed. 1993).

The secondary rubber component of the present invention includes, but isnot limited to at least one or more of brominated butyl rubber,chlorinated butyl rubber, star-branched polyisobutylene rubber,star-branched brominated butyl (polyisobutylene/isoprene copolymer)rubber; halogenated poly(isobutylene-co-p-methylstyrene), such as, forexample, terpolymers of isobutylene derived units, p-methylstyrenederived units, and p-bromomethylstyrene derived units (BrIBMS), and thelike halomethylated aromatic interpolymers as in U.S. Pat. No.5,162,445; U.S. Pat. No. 4,074,035; and U.S. Pat. No. 4,395,506;halogenated isoprene and halogenated isobutylene copolymers,polychloroprene, and the like, and mixtures of any of the above. Someembodiments of the halogenated rubber component are also described inU.S. Pat. No. 4,703,091 and U.S. Pat. No. 4,632,963.

In one embodiment of the invention, a so called semi-crystallinecopolymer (“SCC”) is present as the secondary “rubber” component.Semi-crystalline copolymers are described in WO 00/69966. Generally, theSCC is a copolymer of ethylene or propylene derived units and α-olefinderived units, the α-olefin having from 4 to 16 carbon atoms in oneembodiment, and in another embodiment the SCC is a copolymer of ethylenederived units and α-olefin derived units, the α-olefin having from 4 to10 carbon atoms, wherein the SCC has some degree of crystallinity. In afurther embodiment, the SCC is a copolymer of 1-butene derived units andanother α-olefin derived unit, the other α-olefin having from 5 to 16carbon atoms, wherein the SCC also has some degree of crystallinity. TheSCC can also be a copolymer of ethylene and styrene.

The secondary rubber component of the elastomer composition may bepresent in a range from up to 90 phr in one embodiment, from up to 50phr in another embodiment, from up to 40 phr in another embodiment, andfrom up to 30 phr in yet another embodiment. In yet another embodiment,the secondary rubber is present from at least 2 phr, and from at least 5phr in another embodiment, and from at least 5 phr in yet anotherembodiment, and from at least 10 phr in yet another embodiment. Adesirable embodiment may include any combination of any upper phr limitand any lower phr limit. For example, the secondary rubber, eitherindividually or as a blend of rubbers such as, for example NR and BR,may be present from 5 phr to 90 phr in one embodiment, and from 10 to 80phr in another embodiment, and from 30 to 70 phr in yet anotherembodiment, and from 40 to 60 phr in yet another embodiment, and from 5to 50 phr in yet another embodiment, and from 5 to 40 phr in yet anotherembodiment, and from 20 to 60 phr in yet another embodiment, and from 20to 50 phr in yet another embodiment, the chosen embodiment dependingupon the desired end use application of the composition.

The elastomeric composition may have one or more filler components suchas, for example, calcium carbonate, silica, talc, titanium dioxide, andcarbon black. In one embodiment, the filler is carbon black or modifiedcarbon black, and combinations of any of these. In another embodiment,the filler is a blend of carbon black and silica. The preferred fillerfor such articles as tire treads and sidewalls is reinforcing gradecarbon black present at a level of from 10 to 100 phr of the blend, morepreferably from 30 to 80 phr in another embodiment, and from 50 to 80phr in yet another embodiment. Useful grades of carbon black, asdescribed in RUBBER TECHNOLOGY, 59-85, range from N110 to N990. Moredesirably, embodiments of the carbon black useful in, for example, tiretreads are N229, N351, N339, N220, N234 and N110 provided in ASTM(D3037, D1510, and D3765). Embodiments of the carbon black useful in,for example, sidewalls in tires, are N330, N351, N550, N650, N660, andN762.

The fillers of the present invention may be any size and typicallyrange, for example, from about 0.0001 μm to about 100 μm. As usedherein, silica is meant to refer to any type or particle size silica oranother silicic acid derivative, or silicic acid, processed by solution,pyrogenic or the like methods and having a surface area, includinguntreated, precipitated silica, crystalline silica, colloidal silica,aluminum or calcium silicates, fumed silica, and the like.

One or more crosslinking agents are preferably used in the elastomericcompositions of the present invention, especially when silica is theprimary filler, or is present in combination with another filler. Morepreferably, the coupling agent may be a bifunctional organosilanecrosslinking agent. An “organosilane crosslinking agent” is any silanecoupled filler and/or crosslinking activator and/or silane reinforcingagent known to those skilled in the art including, but not limited to,vinyl triethoxysilane, vinyl-tris-(beta-methoxyethoxy)silane,methacryloylpropyltrimethoxysilane, gamma-amino-propyl triethoxysilane(sold commercially as A1100 by Witco),gamma-mercaptopropyltrimethoxysilane (A189 by Witco) and the like, andmixtures thereof. In one embodiment,bis-(3-triethoxysilypropyl)tetrasulfide (sold commercially as “Si69”) isemployed.

A processing aid may also be present in the composition of theinvention. Processing aids include, but are not limited to,plasticizers, tackifiers, extenders, chemical conditioners, homogenizingagents and peptizers such as mercaptans, petroleum and vulcanizedvegetable oils, mineral oils, parraffinic oils, polybutene oils,naphthenic oils, aromatic oils, waxes, resins, rosins, and the like. Theaid is typically present from 1 to 70 phr in one embodiment, from 3 to60 phr in another embodiment, and from 5 to 50 phr in yet anotherembodiment. Some commercial examples of processing aids are SUNDEX™ (SunChemicals), a naphthenic processing oil, PARAPOL™ (ExxonMobil ChemicalCompany), a polybutene processing oil having a number average molecularweight of from 800 to 3000, and FLEXON™ (ExxonMobil Chemical Company), aparaffinic petroleum oil.

The compositions produced in accordance with the present inventiontypically contain other components and additives customarily used inrubber mixes, such as effective amounts of other nondiscolored andnondiscoloring processing aids, pigments, accelerators, crosslinking andcuring materials, antioxidants, antiozonants. General classes ofaccelerators include amines, guanidines, thioureas, thiazoles, thiurams,sulfenamides, sulfenimides, thiocarbamates, xanthates, and the like.Crosslinking and curing agents include sulfur, zinc oxide, and fattyacids. Peroxide cure systems may also be used. The components, and othercuratives, are typically present from 0.1 to I0 phr in the composition.

Generally, polymer blends, for example, those used to produce. tires,are crosslinked. It is known that the physical properties, performancecharacteristics, and durability of vulcanized rubber compounds aredirectly related to the number (crosslink density) and type ofcrosslinks formed during the vulcanization reaction. (See, e.g., Helt etal., The Post Vulcanization Stabilization for NR in RUBBER WORLD, 18-23(1991). Generally, polymer blends may be crosslinked by adding curativemolecules, for example sulfur, metal oxides, organometallic compounds,radical initiators, etc., followed by heating. In particular, thefollowing metal oxides are common curatives that will function in thepresent invention: ZnO, CaO, MgO, Al₂O₃, CrO₃, FeO, Fe₂O₃, and NiO.These metal oxides can be used alone or in conjunction with thecorresponding metal fatty acid complex (e.g., zinc stearate, calciumstearate, etc.), or with the organic and fatty acids added alone, suchas stearic acid, and optionally other curatives such as sulfur or asulfur compound, an alkylperoxide compound, diamines or derivativesthereof (e.g., DIAK products sold by DuPont). (See also, FormulationDesign and Curing Characteristics of NBR Mixes for Seals, RUBBER WORLD25-30 (1993). This method of curing elastomers may be accelerated and isoften used for the vulcanization of elastomer blends.

The acceleration of the cure process is accomplished in the presentinvention by adding to the composition an amount of an accelerant, oftenan organic compound. The mechanism for accelerated vulcanization ofnatural rubber involves complex interactions between the curative,accelerator, activators and polymers. Ideally, all of the availablecurative is consumed in the formation of effective crosslinks which jointogether two polymer chains and enhance the overall strength of thepolymer matrix. Numerous accelerators are known in the art and include,but are not limited to, the following: stearic acid, diphenyl guanidine(DPG), tetramethylthiuram disulfide (TMTD), 4,4′-dithiodimorpholine(DTDM), tetrabutylthiuran disulfide (TBTD), benzothiazyl disulfide(MBTS), hexamethylene-1,6-bisthiosulfate disodium salt dihydrate (soldcommercially as DURALINK™ HTS by Flexsys), 2-(morpholinothio)benzothiazole (MBS or MOR), blends of 90% MOR and 10% MBTS (MOR 90),N-tertiarybutyl-2-benzothiazole sulfenamide (TBBS), and N-oxydiethylenethiocarbamyl-N-oxydiethylene sulfonamide (OTOS), zinc 2-ethyl hexanoate(ZEH), and “thioureas”.

Functionalized Elastomer

The nanocomposites of the present invention comprise a blend of afunctionalized elastomer and clay, preferably swellable clay, and morepreferably exfoliated clay. Elastomers containing such units asp-alkylstyrene and other styrenic moieties may be functionalized inaccordance with the process of the present invention. Particularlysuitable p-alkylstyrene containing polymers for functionalization arecopolymers of an isoolefin or olefin having from 2 to 7 carbon atoms andap-alkylstyrene, desirablyp-methylstyrene, as described above. In oneembodiment of the present invention it is particularly preferred to usea copolymer of isobutylene and p-methylstyrene.

The foregoing elastomers are functionalized by any suitable techniqueknown in the art that will result in the elastomer having a carboxylicacid moiety or ester moiety pendant to the elastomer polymer chain. Inone embodiment, the elastomer is functionalized by reacting theelastomer, such as, for example, butyl rubber and p-alkylstyrenecontaining polymers or copolymers, with a functionalizing compound inthe presence of an grafting promoter, either as a melt or in thepresence of a diluent, wherein the functionalizing agent is any suitableagent that will facilitate the creation of a carboxylic acid or estergroup pendant to the elastomer. Suitable functionalizing compoundsinclude acid anhydrides, carboxylic acids and acylhalides, typicallyreacted in the presence of a Lewis acid and the elastomer.

For purposes of the present invention, an “grafting promoter” is anelement, compound, reagent, blend of compounds, or apparatus (e.g.,potentiostat) capable of facilitating the grafting of carboxylic acidand/or ester moieties as described above onto an elastomer, particular,elastomers as described herein. Non-limiting examples of graftingpromoters includes Lewis acids and their equivalents, alkali metals, inparticular Li and Na, and alkaline earth metals, in particular Ca.

The functionalized elastomer that results from contacting the graftingpromoter, elastomer and functionalizing compound is an elastomer havingone or more carboxylic acid or ester groups pendant to the elastomerbackbone. These groups pendant to elastomer, E, may be described by anynumber of structures, such as described by one or more of the followinggroups (I), (II), (III), (IV) and (V) pendant to the elastomer, E:

wherein R¹ is selected from hydrogen, C₁ to C₂₀ alkyls, alkenyls oraryls, substituted C₁ to C₂₀ alkyls, alkenyls or aryls; wherein thevalue of x ranges from 0 to 20, preferably from 1 to 10, and morepreferably from 1 to 5; and wherein the value of y ranged from 0 to 20,preferably from 0 to 10; and wherein the value of z ranges from 1 to 20,preferably from 1 to 10, and more preferably from 1 to 5; and wherein“A” is an aryl group, either substituted or not.

Preferably, R¹ is selected from hydrogen, C₁ to C₆ alkyls, alkenyls andaryls, substituted C₁ to C₈ alkyls, alkenyls and aryls, hydroxyl, and C₁to C₈ alkoxys.

Any part of the elastomer, any monomer unit or any moiety pendant to theelastomer may be functionalized as a result of the functionalization. Inone embodiment, the styrenic or substituted styrenic derived unit of theelastomer, when present, is the functionalized monomer unit.

The functionalizing compound includes any compound that will eitherfacilitate the addition or “grafting” of the groups represented by (I)through (V) onto the elastomer of the invention or a compound thatitself is grafted onto the elastomer. In one aspect of the invention,the functionalizing compound is selected from CO₂ and the following (VI)and (VII):

wherein R² and R³ are the same or different and are selected fromhydrogen, C₁ to C₁₀ alkyls, alkenyls and aryls, hydroxyl, and C₁to C₁₀alkoxys, wherein R² and R³ may form a ring structure; and wherein X isselected from hydroxyl and halides, preferably bromine and chlorine, andalkoxy groups. Suitable alkoxy groups are such groups as —OCH₃,—OCH₂CH₃, —OCH₂CH₂CH₃, —OCH₂(CH₃)CH₃, etc.

Non-limiting examples of functionalizing compounds include acidanhydrides and acylhalides. Particularly useful anhydrides includesuccinic anhydride, maleic anhydride, phthalic anhydride, glutaricanhydride, citraconic anhydride, itaconic anhydride, and other cyclicanhydrides, and mixtures thereof.

Particularly useful acylhalides include succinyl chloride, glutarylchloride, itaconyl chloride, malonyl chloride, adipoyl chloride,diethylmalonyl dichloride, 3-methyladipoyl chloride, pimeloyl chloride,suberoyl chloride, azelaoyl chloride, sebacoyl chloride, isophthaloyldichloride, phthaloyldichloride, terephthaoyl chloride and mixturesthereof.

In one embodiment, the acylhalide will have from 2 to 14 carbon atomsand the acid anhydride will have from 4 to 12 carbon atoms.

A suitable Lewis acid catalyst can be used in preparing thefunctionalized elastomers; desirable Lewis acid catalysts are based onmetals such as boron, aluminum, gallium, indium, titanium, zirconium,tin, arsenic, antimony and bismuth. Especially preferred are the halidecontaining compounds of the foregoing metals such as boron trifluoride,aluminum trichloride, aluminum dichloride and the like.

In one embodiment, the functionalization will be carried out in thepresence of a hydrocarbon diluent such as aliphatic hydrocarbons or inthe presence of a polar solvent such as carbon disulfide, nitrobenzene,methylene chloride and 1,2 dichloroethane and the like. In anotherembodiment of the present invention it is desirable to carry out theprocess as a melt blend at a temperature wherein the elastomer exists asa molten or semi-molten state, or from 0 to 200° C. in one embodiment,and from 20 to 180° C. in another embodiment.

The functionalization of the polymers typically is carried out attemperatures of from −50° C. to 150° C., for times sufficient to add thefunctional group, that is, the alkyl carbonyl, alkenyl carboxylic acid,to the aromatic ring of the p-alkylstyrene containing polymer.

The ratio of functionalizing compound, such as the acylhalide or acidanhydride, to the styrenic units in the p-alkylstyrene containingpolymer can vary widely. In general, however, from 0.01 to 10 moles ofacylhalide or acid anhydride or unsaturated anhydride per 1 mole ofstyrenic moieties in the styrene containing polymer will be employed.

For elastomers containing p-methylstyrene, the benzyl group can beoxidized in the presence of an oxidizing agent to produce carboxylicacid on the elastomer (structure I, X=0). In another embodiment thebenzyl group can react with an alkali metal such as Li, then CO₂ withprotonation to produce carboxylic acid on the elastomer (structure I,X=0). Both of these functional polymers can also be used for thenanocomposite preparation disclosed herein.

The functional groups “grafted” onto the elastomer backbone may bepresent from 0.01 wt %. to 15 wt %, by weight of the graftedfunctionalized (or “grafted”) elastomer in one embodiment, and from 0.05wt % to 10 wt % in another embodiment, and from 0.1 wt % to 8 wt % inyet another embodiment.

One aspect of the invention just described is a nanocomposite comprisingclay and an elastomer comprising C₂ to C₁₀ olefin derived units; whereinthe elastomer comprises functionalized monomer units described by thefollowing groups (I), (II), (III), (IV) and (V) pendant to theelastomer, E:

wherein R¹ is selected from hydrogen, C₁ to C₂₀ alkyls, alkenyls oraryls, substituted C₁ to C₂₀ alkyls, alkenyls or aryls; wherein thevalue of x ranges from 0 to 20, preferably from 1 to 10, and morepreferably from 1 to 5; and wherein the value of y ranged from 0 to 20,preferably from 0 to 10; and wherein the value of z ranges from 1 to 20,preferably from 1 to 10, and more preferably from 1 to 5; and wherein“A” is an aryl group, either substituted or not.

Alternately, the nanocomposite of the invention can be described ascomprising clay and the reaction product of contacting an elastomercomprising C₂ to C₁₀ olefin derived units, a grafting promoter and atleast one functionalizing compound. The product of contacting theelastomer and the functionalizing compound and grafting promoter may bedescribed as an elastomer having one or more carboxylic acid and (or) anester moieties pendant to the elastomer in one embodiment, or describedas any one or more of structures (I) through (IV) above. The amount offunctionalization (or number of functionalized units) is from 0.01 wt %to 15 wt % in one embodiment, and other ranges as described herein.

In one embodiment of the invention, the elastomer also comprises styrenederived units, alkylstyrene derived units in one embodiment,p-alkylstyrene derived units in another embodiment. In anotherembodiment, the elastomer comprises a group selected fromα-methylstyrene, o-methylstyrene, m-methylstyrene, and p-methylstyreneunits. In yet another embodiment, the elastomer ispoly(isobutylene-co-p-methylstyrene). And in yet another embodiment, theelastomer is a terpolymer comprising ethylene derived units, propylenederived units, and styrene derived units. And in yet another embodiment,the elastomer is a terpolymer comprising ethylene derived units,propylene derived units, and p-methylstyrene derived units. Whenpresent, the elastomer comprises from 1 wt % to 15 wt % by weight of theelastomer of the p-alkylstyrene derived unit, p-methylstyrene in oneembodiment.

In another embodiment, the elastomer also comprises monomer unitsselected from styrenic derived units and substituted styrenic derivedunits.

In yet another embodiment of the elastomer, the olefin is selected fromone or more of isobutylene, isobutene, 2-methyl-1-butene,3-methyl-1-butene, 2-methyl-2-butene, and 4-methyl-1-pentene, ethylene,propene, 1-butene, 1-hexene, and 1-octene.

In yet another embodiment of the elastomer, the styrene derived unitsare present from 1 to 15 wt % of the elastomer when present.

In yet another embodiment of the elastomer, the elastomer comprisesp-methylstyrene derived units.

In yet another embodiment of the elastomer, the elastomer also comprisesisoolefin derived units and p-methylstyrene derived units.

In yet another embodiment of the elastomer, the elastomer also comprisesmultiolefin derived units.

In one embodiment of the invention, the functionalized units are presenton the elastomer from 0.01 wt % to 15 wt % of the elastomer.

In yet another embodiment, the elastomer is selected from any one or amixture of natural rubber, poly(isobutylene-co-isoprene), polybutadiene,poly(styrene-co-butadiene) rubber, poly(isoprene-co-butadiene),poly(styrene-isoprene-butadiene), star-branched polyisobutylene rubber,poly(isobutylene-co-p-methylstyrene), ethylene-propylene-alkylstyrenerubber, ethylene-propylene-styrene rubber; and from any one or a mixtureof poly(isobutylene-co-isoprene), polybutadiene,poly(styrene-co-butadiene) rubber, poly(isoprene-co-butadiene),poly(styrene-isoprene-butadiene), star-branched polyisobutylene rubber,poly(isobutylene-co-p-methylstyrene), ethylene-propylene-alkylstyrenerubber, ethylene-propylene-styrene rubber in another embodiment.

In one embodiment, the clay is swellable, and exfoliated in anotherembodiment, wherein the clay has been treated with an exfoliating agentto form an exfoliated clay. In the embodiment where the clay isexfoliated, the exfoliating agent may be selected from ammonium ion,alkylamines, alkylammonium ion (primary, secondary, tertiary andquaternary), phosphonium or sulfonium derivatives of aliphatic, aromaticor arylaliphatic amines, phosphines and sulfides and blends thereof.

The clay is present from 0.1 wt % to 50 wt % of the nanocomposite in oneembodiment; and present from 0.5 wt % to 15 wt % of the nanocomposite inanother embodiment; and present from 1 wt % to 30 wt % of thenanocomposite in yet another embodiment.

The nanocomposite may also comprise other components such as a fillerselected from carbon black, modified carbon black, silica, precipitatedsilica, and blends thereof.

Further, the nanocomposite may also comprise one or more curing agents,wherein the curing agent is selected from zinc, zinc stearate, fattyacids, sulfur, diamine, diepoxy, polyamine, polyepoxy and mixturesthereof.

Further, the nanocomposite may also comprise a secondary rubber or“general purpose rubber”, the secondary rubber selected from naturalrubber, polybutadiene rubber, nitrile rubber, silicon rubber,polyisoprene rubber, poly(styrene-co-butadiene) rubber,poly(isoprene-co-butadiene) rubber, styrene-isoprene-butadiene rubber,ethylene-propylene rubber, brominated butyl rubber, chlorinated butylrubber, halogenated isoprene, halogenated isobutylene copolymers,polychloroprene, star-branched polyisobutylene rubber, star-branchedbrominated butyl rubber, poly(isobutylene-co-isoprene) rubber;halogenated poly(isobutylene-co-p-methylstyrene), ethylene-propylenerubber and mixtures thereof.

In one aspect of the invention, the nanocomposite is formed using anysuitable method known in the art into an air barrier such as aninnerliner or innertube suitable for vehicle tires, truck tires,automotive and motorcycle tires, and other tires.

The invention also includes a method of forming a nanocompositecomprising contacting clay, an elastomer, an grafting promoter, and atleast one functionalizing compound, wherein the elastomer comprises C₂to C₁₀ olefin derived units.

In one embodiment, the elastomer is first contacted with thefunctionalizing compound, followed by contacting with the clay. Inanother embodiment, the elastomer, clay and acid functionalizingcompound are contacted simultaneously.

In one embodiment, the grafting promoter is a Lewis acid selected fromhalide and alkyl containing compounds of boron, aluminum, gallium,indium, titanium, zirconium, tin, arsenic, antimony and bismuth, andmixtures thereof.

In yet another embodiment, the method comprises contacting a diluentselected from carbon disulfide, nitrobenzene, methylene chloride, 1,2dichloroethane, hexane, cyclohexane and mixtures thereof.

In yet another embodiment, the elastomer and functionalizing compoundare melt blended, thus forming the functionalized elastomer.

In one embodiment, functionalizing compound is selected from CO₂ and thefollowing structures:

wherein R² and R³ are the same or different and are selected fromhydrogen, C₁ to C₁₀ alkyls, alkenyls and aryls, hydroxyl, and C₁ to C₁₀alkoxys, wherein R² and R³ may form a ring structure; and wherein X isselected from hydroxyl and halides, preferably bromine and chlorine, andalkoxy groups. In another embodiment, R₂ and R₃ are the same ordifferent and are selected from hydrogen, C₁ to C₈ alkyls, alkenyls andaryls, wherein R₂ and R₃ may form 4 to 6 member ring structures such asmaleic anhydride, succinic anhydride, phthalic anhydride and substitutedderivatives thereof.

The following examples illustrate the invention:

Test Methods

Permeability Testing.

All specimens were compression molded with slow cooling to providedefect free pads. A compression and curing press was used for rubbersamples. Typical thickness of a compression molded pad is about 15 mil.using an Arbor press, 2″ diameter disks were then punched out frommolded pads for permeability testing. These disks were conditioned in avacuum oven at 60° C. overnight prior to the measurement. The oxygenpermeation measurements were done using a Mocon OX-TRAN 2/61permeability tester at 40° C. under the principle of R. A. Pasternak et.al. in 8 JOURNAL OF POLYMER SCIENCE: PART A-2 467 (1970). Disks thusprepared were mounted on a template and sealed with a vacuum grease. 10psi nitrogen was kept on one side of the disk, whereas the other side is10 psi oxygen. Using the oxygen sensor on the nitrogen side, increase inoxygen concentration on the nitrogen side with time could be monitored.The time required for oxygen to permeate through the disk, or for oxygenconcentration on the nitrogen side to reach a constant value, isrecorded and used to determine the oxygen permeability.

XRD Measurement.

The average d-spacing between clay plates in the final composite ismeasured by standard small angle X-Ray Instrumentation using 2D AreaDetector System. The scan range is 0 to 10°, 2θ and collection time of900 seconds.

EXAMPLES

The present invention, while not meant to be limiting by, may be betterunderstood by reference to the following example and Tables.

As a comparative example (Example 1), the permeability ofpoly(isobutylene-co-p-methylstyrene) (“XP 50”) comprising 11.5 wt %p-methylstyrene units by weight of the polymer was measured. Thepermeability data are summarized in Table 2.

In example 2, the elastomer XP-50 containing 11.5 wt % p-methylstyrene(55 g) and succinic anhydride (3 g) were dissolved in methylene chloride(CH₂Cl₂). To the solution was added AlCl₃ (8 g). After being stirred for1.5 hours, the solution was poured into methanol containing 120 mmol HClto afford the functionalized elastomer. Next, the functionalizedelastomer (40.5 g) was melt blended in a Brabender at 160° C., followedby addition of Cloisite 6A clay (4.5 g) and mixing for 10 min. A sampleof this composition was pressed into a film tested for permeability.These data are summarized in Table 2. An unpressed sample was measuredfor d-spacings. The clay d-spacings from XRD measurements was 5.04 nm.

Thus the d-spacing of clay in nanocomposite (Example 2) is much largerthan that (3.60 nm) of original Cloisite 6A. The significant increase ofthe clay d-spacing after nanocomposite formation indicates a strongintecalant or exfoliation took place.

For Example 3, XP 50 containing 11.5 % p-methylstyrene (55 g) andsuccinic anhydride (1.0 g) were dissolved in CH₂Cl₂. To this solutionwas added AlCl₃ (2.7 g). After being stirred for 1.5 hours, the solutionwas poured into methanol containing 100 mmol HCl and the obtainedproduct was washed with acetone and dried under vacuum overnight. Next,the modified product was melt blended in a Brabender at 160° C. andmixed with 4.5 g of clay (Cloisite 6A) for 10 minutes at a rotor speedof 60 rpm. A sample of this composition was tested for permeability,data for which is summarized in Table 2.

For Example 4, XP 50 containing 11.5% p-methylstyrene (75 g) andsuccinic anhydride (1.03 g) was dissolved in CH₂Cl₂. To this solutionwas added AlCl₃ (2.8 g). After being stirred for 1.5 hours, the solutionis poured into methanol containing 100 mmol HCl and the obtained productwas washed with acetone and dried under vacuum overnight. Then thefunctionalized elastomer was melt blended in a Brabender at 160° C. andmixed with 4.5 g of clay (Cloisite 6A) for 10 minutes at a rotor speedof 60 rpm. A sample of this composition was tested for permeability and,data for which is summarized in Table 2.

Example 5 illustrates the use of functionalized polymer in blendapplication. For example 5, the following procedure was carried out:Butyl rubber (XP50, 31.5 grams) and modified butyl (9.0 grams) fromexample 2 were melt in Brabender for three minutes with a rotor speed of60 rpm at 160° C. To the melt was added Cloisite 6A (4.5 grams). Themixture was further mixed for 10 minutes. A sample of this compositionwas tested for permeability and, data for which is summarized in Table2.

Nanocomposites of the present invention have a permeation coefficient ofless than 7 mm·cc/(m²·day·mmHg) at 40° C. in one embodiment, and lessthan 6 mm·cc/(m²·day·mmHg) at 40° C. in another embodiment, and lessthan 5 mm·cc/(m²·day·mmHg) at 40° C. in yet another embodiment, andbetween 2 and 7 mm·cc/(m²·day·mmHg) at 40° C. in yet another embodiment.

While the present invention has been described and illustrated byreference to particular embodiments, those of ordinary skill in the artwill appreciate that the invention lends itself to many differentvariations not illustrated herein. For these reasons, then, referenceshould be made solely to the appended claims for purposes of determiningthe scope of the present invention. Further, certain features of thepresent invention are described in terms of a set of numerical upperlimits and a set of numerical lower limits. It should be appreciatedthat ranges formed by any combination of these limits are within thescope of the invention unless otherwise indicated.

All priority documents are herein fully incorporated by reference forall jurisdictions in which such incorporation is permitted. Further, alldocuments cited herein, including testing procedures, are herein fullyincorporated by reference for all jurisdictions in which suchincorporation is permitted. TABLE 1 Material Description ComponentDescription Material Source maleic “functionalizing compound” AldrichChemical anhydride Company methylene CH₂CI₂ Aldrich Chemical chlorideCompany succinic “functionalizing compound” Aldrich Chemical anhydrideCompany 6A Montmorillonite clay treated with Cloisite 6A, di-methyldi-hydrogenated tallow Southern Clay alkyl ammonia chloride

TABLE 2 Permeability data¹ permeation grafted coefficientfunctionalizing functional unit (mm · cc/ compound (wt % relative to (m²· day · mm Example (grams) elastomer) Hg)) at 40° C. 1 (comp.) — — 7.672 succinic anhydride 2.4 3.60 (3.0 g)  3 succinic anhydride 0.71 3.85(1.0 g)  4 succinic anhydride 0.48 4.46 (1.03 g) 5 — — 5.70¹all samples were dried under vacuum prior to permeation measurements.

1. A nanocomposite comprising clay and an elastomer comprising C₂ to C₁₀olefin derived units; wherein the elastomer also comprisesfunctionalized monomer units described by the following groups (I),(II), (III), (IV) and (V) pendant to the elastomer, E:

wherein R¹ is selected from hydrogen, C₁ to C₂₀ alkyls, alkenyls oraryls, substituted C₁ to C₂₀ alkyls, alkenyls or aryls; wherein thevalue of x ranges from 0 to 20, preferably from 1 to 10, and morepreferably from 1 to 5; and wherein the value of y ranged from 0 to 20,preferably from 0 to 10; and wherein the value of z ranges from 1 to 20,preferably from 1 to 10, and more preferably from 1 to 5; and wherein“A” is an aryl group, either substituted or not.
 2. The nanocomposite ofclaim 1, wherein the elastomer also comprises monomer units selectedfrom styrenic derived units and substituted styrenic derived units. 3.The nanocomposite of claim 2, wherein the styrenic units arefunctionalized.
 4. The nanocomposite of claim 1, wherein the elastomeris not halogenated.
 5. The nanocomposite of claim 1, wherein the olefinis selected from one or more of isobutylene, isobutene, isoprene,cyclopentadiene, 2-methyl-1-butene, 3-methyl-1 -butene,2-methyl-2-butene, and 4-methyl-1-pentene, ethylene, propene, 1-butene,1-hexene, and 1-octene.
 6. The nanocomposite of claim 2, wherein thestyrene derived units are present from I to 15 wt % of the elastomer. 7.The nanocomposite of claim 1, wherein the elastomer comprisesp-methylstyrene derived units.
 8. The nanocomposite of claim 1, whereinthe elastomer also comprises isoolefin derived units and p-methylstyrenederived units.
 9. The nanocomposite of claim 1, wherein the elastomeralso comprises multiolefin derived units.
 10. The nanocomposite of claim1, wherein the elastomer is selected from any one or a mixture ofnatural rubber, poly(isobutylene-co-isoprene), polybutadiene,poly(styrene-co-butadiene) rubber, poly(isoprene-co-butadiene),poly(styrene-isoprene-butadiene), star-branched polyisobutylene rubber,poly(isobutylene-co-p-methylstyrene), ethylene-propylene-alkylstyrenerubber, ethylene-propylene-styrene rubber.
 11. The nanocomposite ofclaim 1, wherein the functionalized units are present on the elastomerfrom 0.01 wt % to 15 wt % of the elastomer.
 12. The nanocomposite ofclaim 1, wherein the clay has been treated with an exfoliating agent toform an exfoliated clay.
 13. The nanocomposite of claim 12, wherein theexfoliating agent is selected from ammonium ion, alkylamines,alkylammonium ion (primary, secondary, tertiary and quaternary),phosphonium or sulfonium derivatives of aliphatic, aromatic orarylaliphatic amines, phosphines and sulfides and blends thereof. 14.The nanocomposite of claim 1, wherein the clay is present from 0.1 wt %to 50 wt % of the nanocomposite.
 15. The nanocomposite of claim 1,wherein the clay is present from 0.5 wt % to 15 wt % of thenanocomposite.
 16. The nanocomposite of claim 1, also comprising afiller selected from carbon black, modified carbon black, silica,precipitated silica, and blends thereof.
 17. The nanocomposite of claim1, also comprising one or more curing agents.
 18. The nanocomposite ofclaim 17, wherein the curing agent is selected from zinc, zinc stearate,fatty acids, sulfur, diamine, diepoxy, polyamine, polyepoxy and mixturesthereof.
 19. The nanocomposite of claim 1, also comprising a secondaryrubber selected from natural rubber, polybutadiene rubber, nitrilerubber, silicon rubber, polyisoprene rubber, poly(styrene-co-butadiene)rubber, poly(isoprene-co-butadiene) rubber, styrene-isoprene-butadienerubber, ethylene-propylene rubber, brominated butyl rubber, chlorinatedbutyl rubber, halogenated isoprene, halogenated isobutylene copolymers,polychloroprene, star-branched polyisobutylene rubber, star-branchedbrominated butyl rubber, poly(isobutylene-co-isoprene) rubber;halogenated poly(isobutylene-co-p-methylstyrene), ethylene-propylenerubber and mixtures thereof.
 20. A tire innerliner comprising thenanocomposite of claim
 1. 21. An innertube comprising the nanocompositeof claim
 1. 22. A method of forming a nanocomposite comprisingcontacting clay, an elastomer, an grafting promoter, and at least onefunctionalizing compound, wherein the elastomer comprises C₂ to C₁₀olefin derived units.
 23. The method of claim 22, wherein the elastomeris first contacted with the functionalizing compound, followed bycontacting with the clay.
 24. The method of claim 22, wherein theelastomer, clay and acid functionalizing compound are contactedsimultaneously.
 25. The method of claim 22, wherein the graftingpromoter is a Lewis acid selected from halide and alkyl containingcompounds of boron, aluminum, gallium, indium, titanium, zirconium, tin,arsenic, antimony and bismuth, and mixtures thereof.
 26. The method ofclaim 22, further comprising contacting a diluent selected from carbondisulfide, nitrobenzene, methylene chloride, 1,2 dichloroethane, hexane,cyclohexane and mixtures thereof.
 27. The method of claim 22, whereinthe elastomer and functionalizing compound are melt blended.
 28. Themethod of claim 22, wherein the functionalizing compound is selectedfrom CO₂ and the following:

wherein R² and R³ are the same or different and are selected fromhydrogen, C₁ to C₁₀ alkyls, alkenyls and aryls, hydroxyl, and C₁ to C₁₀alkoxys, wherein R² and R³ may form a ring structure; and wherein X isselected from hydroxyl, halides, preferably bromine and chlorine, andalkoxy groups.
 29. The method of claim 22, wherein the functionalizingcompound is selected from succinic anhydride, maleic anhydride, phthalicanhydride, glutaric anhydride citraconic anhydride, itaconic anhydride,and other cyclic anhydrides, succinyl chloride, glutaryl chloride,itaconyl chloride, malonyl chloride, adipoyl chloride, diethylmalonyldichloride, 3-methyladipoyl chloride, pimeloyl chloride, suberoylchloride, azelaoyl chloride, sebacoyl chloride, isophthaloyl dichloride,phthaloyldichloride, terephthaoyl chloride.
 30. The method of claim 22,wherein the elastomer also comprises monomer units selected fromstyrenic derived units and substituted styrenic derived units.
 31. Themethod of claim 22, wherein the olefin is selected from one or more ofisobutylene, isobutene, isoprene, cyclopentadiene, 2-methyl-1-butene,3-methyl-1-butene, 2-methyl-2-butene, and 4-methyl-1-pentene, ethylene,propene, 1-butene, 1-hexene, and 1-octene.
 32. The method of claim 30,wherein the styrene derived units are present from 1to 15 wt % of theelastomer.
 33. The method of claim 22, wherein the elastomer comprisesp-methylstyrene derived units.
 34. The method of claim 22, wherein theelastomer also comprises isoolefin derived units and p-methylstyrenederived units.
 35. The method of claim 22, wherein the elastomer alsocomprises multiolefin derived units.
 36. The method of claim 22, whereinthe elastomer is selected from any one or a mixture of natural rubber,poly(isobutylene-co-isoprene), polybutadiene, poly(styrene-co-butadiene)rubber, poly(isoprene-co-butadiene), poly(styrene-isoprene-butadiene),star-branched polyisobutylene rubber,poly(isobutylene-co-p-methylstyrene), ethylene-propylene-alkylstyrenerubber, ethylene-propylene-styrene rubber.
 37. The method of claim 22,wherein the elastomer is functionalized by contacting with thefunctionalizing compound, wherein the functional groups are present onthe elastomer from 0.01 wt % to 15 wt % of the elastomer.
 38. The methodof claim 22, wherein the clay has been treated with an exfoliating agentto form an exfoliated clay.
 39. The method of claim 38, wherein theexfoliating agent is selected from ammonium ion, alkylamines,alkylammonium ion (primary, secondary, tertiary and quaternary),phosphonium or sulfonium derivatives of aliphatic, aromatic orarylaliphatic amines, phosphines and sulfides and blends thereof. 40.The method of claim 22, wherein the clay is present from 0.1 wt % to 50wt % of the nanocomposite.
 41. The method of claim 22, wherein the clayis present from 0.5 wt % to 15 wt % of the nanocomposite.
 42. The methodof claim 22, also comprising a filler selected from carbon black,modified carbon black, silica, precipitated silica, and blends thereof.43. The method of claim 22, also comprising one or more curing agents.44. The method of claim 43, wherein the curing agent is selected fromzinc, zinc stearate, fatty acids, sulfur, diamine, diepoxy, polyamine,polyepoxy and mixtures thereof.
 45. The method of claim 22, alsocomprising a secondary rubber selected from natural rubber,polybutadiene rubber, nitrile rubber, silicon rubber, polyisoprenerubber, poly(styrene-co-butadiene) rubber, poly(isoprene-co-butadiene)rubber, styrene-isoprene-butadiene rubber, ethylene-propylene rubber,brominated butyl rubber, chlorinated butyl rubber, halogenated isoprene,halogenated isobutylene copolymers, polychloroprene, star-branchedpolyisobutylene rubber, star-branched brominated butyl rubber,poly(isobutylene-co-isoprene) rubber; halogenatedpoly(isobutylene-co-p-methylstyrene), ethylene-propylene rubber andmixtures thereof.
 46. A tire innerliner made by the method of claim 22.47. An innertube made by the method of claim
 22. 48. A nanocompositecomprising clay and the reaction product of contacting an elastomercomprising C₂ to C₁₀ olefin derived units, an grafting promoter, and atleast one functionalizing compound.
 49. The nanocomposite of claim 48,wherein the functionalizing compound is selected from CO₂ and thefollowing:

wherein R² and R³ are the same or different and are selected fromhydrogen, C₁ to C₁₀ alkyls, alkenyls and aryls, hydroxyl, and C₁ to C₁₀alkoxys, wherein R² and R³ may form a ring structure; and wherein X isselected from hydroxyl, halides, preferably bromine and chlorine, andalkoxy groups.
 50. The nanocomposite of claim 48, wherein thefunctionalizing compound is selected from succinic anhydride, maleicanhydride, phthalic anhydride, glutaric anhydride citraconic anhydride,itaconic anhydride, and other cyclic anhydrides, succinyl chloride,glutaryl chloride, itaconyl chloride, malonyl chloride, adipoylchloride, diethylmalonyl dichloride, 3-methyladipoyl chloride, pimeloylchloride, suberoyl chloride, azelaoyl chloride, sebacoyl chloride,isophthaloyl dichloride, phthaloyldichloride, terephthaoyl chloride. 51.The nanocomposite of claim 48, wherein the grafting promoter is a Lewisacid selected from halide and alkyl containing compounds of boron,aluminum, gallium, indium, titanium, zirconium, tin, arsenic, antimonyand bismuth, and mixtures thereof.
 52. The nanocomposite of claim 48,wherein the components are contacted in a diluent selected from carbondisulfide, nitrobenzene, methylene chloride, 1,2 dichloroethane, hexane,cyclohexane and mixtures thereof.
 53. The nanocomposite of claim 48,wherein the elastomer also comprises monomer units selected fromstyrenic derived units and substituted styrenic derived units.
 54. Thenanocomposite of claim 53, wherein the styrenic units arefunctionalized.
 55. The nanocomposite of claim 48, wherein the elastomeris not halogenated.
 56. The nanocomposite of claim 48, wherein theolefin is selected from one or more of isobutylene, isobutene,2-methyl-1-butene, 3-methyl-1-butene, 2-methyl-2-butene, and4-methyl-1-pentene, ethylene, propene, 1-butene, 1-hexene, and 1-octene.57. The nanocomposite of claim 53, wherein the styrene derived units arepresent from 1 to 15 wt % of the elastomer.
 58. The nanocomposite ofclaim 48, wherein the elastomer comprises p-methylstyrene derived units.59. The nanocomposite of claim 48, wherein the elastomer also comprisesisoolefin derived units and p-methylstyrene derived units.
 60. Thenanocomposite of claim 48, wherein the elastomer also comprisesmultiolefin derived units.
 61. The nanocomposite of claim 48, whereinthe elastomer is selected from any one or a mixture of natural rubber,poly(isobutylene-co-isoprene), polybutadiene, poly(styrene-co-butadiene)rubber, poly(isoprene-co-butadiene), poly(styrene-isoprene-butadiene),star-branched polyisobutylene rubber,poly(isobutylene-co-p-methylstyrene), ethylene-propylene-alkylstyrenerubber, ethylene-propylene-styrene rubber.
 62. The nanocomposite ofclaim 48, wherein the functionalized derived units are present on theelastomer from 0.01 wt % to 15 wt % of the elastomer.
 63. Thenanocomposite of claim 48, wherein the clay has been treated with anexfoliating agent to form an exfoliated clay.
 64. The nanocomposite ofclaim 63, wherein the exfoliating agent is selected from ammonium ion,alkylamines, alkylammonium ion (primary, secondary, tertiary andquaternary), phosphonium or sulfonium derivatives of aliphatic, aromaticor arylaliphatic amines, phosphines and sulfides and blends thereof. 65.The nanocomposite of claim 48, wherein the clay is present from 0.1 wt %to 50 wt % of the nanocomposite.
 66. The nanocomposite of claim 48,wherein the clay is present from 0.5 wt % to 15 wt % of thenanocomposite.
 67. The nanocomposite of claim 48, also comprising afiller selected from carbon black, modified carbon black, silica,precipitated silica, and blends thereof.
 68. The nanocomposite of claim48, also comprising one or more curing agents.
 69. The nanocomposite ofclaim 68, wherein the curing agent is selected from zinc, zinc stearate,fatty acids, sulfur, diamine, diepoxy, polyamine, polyepoxy and mixturesthereof.
 70. The nanocomposite of claim 48, also comprising a secondaryrubber selected from natural rubber, polybutadiene rubber, nitrilerubber, silicon rubber, polyisoprene rubber, poly(styrene-co-butadiene)rubber, poly(isoprene-co-butadiene) rubber, styrene-isoprene-butadienerubber, ethylene-propylene rubber, brominated butyl rubber, chlorinatedbutyl rubber, halogenated isoprene, halogenated isobutylene copolymers,polychloroprene, star-branched polyisobutylene rubber, star-branchedbrominated butyl rubber, poly(isobutylene-co-isoprene) rubber;halogenated poly(isobutylene-co-p-methylstyrene) and mixtures thereof.71. A tire innerliner comprising the nanocomposite of claim
 48. 72. Aninnertube comprising the nanocomposite of claim 48.